Cameron Monaghan Is Leaving 'Shameless' Monaghan, who plays br "Ian Gallagher" on 'Shameless', took br to Instagram to tell fans that he will br be leaving the show after the next episode. Cameron Monaghan, via Instagram Monaghan went on to say that he had been planning to leave the show since last year but kept quiet in order to preserve the storyline for fans. Cameron Monaghan, via Instagram Monaghan is the second 'Shameless' br star to announce their departure br from the hit Showtime series. Emmy Rossum, who plays br "Fiona Gallagher," previously br announced that the current br ninth season would be her last.